Reverse wound electrodes

ABSTRACT

An implantable lead includes an insulative sheath and a coil member; the coil member including a conductor wound from a proximal end of the coil member to a distal end and reverse wound back toward the proximal end to form an electrode on an outer diameter of the coil member adjacent and distal to the insulative sheath.

FIELD OF THE INVENTION

[0001] This invention relates to implantable devices and moreparticularly relates to the design and manufacture of implantable leads.

BACKGROUND OF THE INVENTION

[0002] In the traditional forming of implantable medical electricalleads, one or more wires are wound on a mandrel so as to form a coil.The wires are wrapped with enough tension to cause the wires to exceedtheir yield point and thus to hold a coiled shape. The pitch of a coilmay range from close wound, that approaching the wire diameter or thesum of the wire diameters, for multi-wire coils, to space wound, thatexceeding the wire diameter or sum of the wire diameters. The coil maybe one of several conductors included in an implantable lead body andthe coil may be formed from multiple insulated wires as amulti-conductor coil. The lead body is usually constructed having anouter polymeric sheath encasing the conductors, which may be arrangedcoaxially or co-linearly and are insulated from one another. A distalend of each conductor is coupled to one or more electrodes while aproximal end of each conductor is coupled to a contact of a connectorthat is in turn coupled to an implantable pulse generator (IPG) or animplantable cardioverter defibrillator (ICD). The distal end of the leadis implanted to be positioned within the heart so that the electrodesmay deliver pacing and or defibrillation therapy by both sensingelectrical activity of the heart muscle and stimulating the heartmuscle.

[0003] Each conductor is typically coupled to a corresponding electrode,which has been formed as a separate component, such as a ring electrode,a coil electrode or a tip electrode. In designing and constructingjoints between the conductors and the electrodes care must be taken toform reliable mechanical and electrical coupling; it is also desirablethat the joints do not increase the profile of the lead body.Eliminating as many joints as is practical in the construction of a leadmay improve the reliability of the lead and increase the ease ofmanufacturing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004]FIG. 1A is a plan view of a coil according to one embodiment ofthe present invention.

[0005]FIG. 1B is a plan view of a multi-conductor coil according on oneembodiment of the present invention.

[0006]FIG. 1C is a plan view of a multi-conductor coil according toanother embodiment of the present invention.

[0007]FIG. 1D is a partial section plan view of the multi-conductor coilof FIG. 1C.

[0008]FIG. 2A is a partial section plan view of an implantable leadincorporating the coil from FIG. 1A.

[0009]FIG. 2B is a cross-sectional plan view of a distal end of analternate embodiment of a lead incorporating the coil from FIG. 1A

[0010]FIG. 3 is a cross-sectional plan view of a distal end of analternate embodiment of a lead incorporating the coil from FIG. 1B

[0011]FIG. 4 is a partial section plan view of a lead incorporating thecoil from FIG. 1C-D

[0012] FIGS. 5-8 are schematics depicting several embodiments ofimplantable leads according to the present invention joined to animplantable medical device and implanted in exemplary locations within aheart.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The following detailed description is to be read with referenceto the figures, in which like elements in different figures have likereference numerals. The figures, which are not necessarily to scale,depict selected embodiments and are not intended to limit the scope ofthe invention. Embodiments of the present invention may be employed inmany various types of devices, such as pacemakers, cardioverterdefibrillators, and neurostimulators, for treating patient medicalconditions. Skilled artisans will recognize that the examples providedherein have many useful alternatives that fall within the scope of theinvention.

[0014]FIG. 1A is a plan view of a coil 50 according to one embodiment ofthe present invention. Coil 50 is incorporated into embodiments ofmedical electrical leads according to the present invention asillustrated in FIGS. 2A and 2B. As illustrated in FIG. 1A, coil 50includes a wound conductor 51 and an electrode 53 at a distal end 54;wound conductor 51 forming an outer diameter 52 of coil 50 and a reversewound portion of conductor 51, over outer diameter 52, forming electrode53. Coil 50 may be formed using a programmable coil winder, known tothose skilled in the art, winding in a first direction “A” and thenreverse winding in a second direction “B” to form electrode 53 overouter diameter 52. Conductor 51 and all other conductors presentedherein for alternate embodiments are formed from any material capable ofreliably conducting electrical current after having been subjected tonumerous repetitive bending and torsional stresses, examples of suchmaterials include tantalum, MP35-N alloy, platinum, Elgiloy, andstainless steel. Conductor 51 and all other conductors illustratedherein in various embodiments include a single wire, however, inalternate embodiments, a conductor includes a plurality of common wires;anywhere from two to six wires, depending on the application, perconductor are contemplated. Furthermore, alternate embodiments includecomposite wires formed of any of the preceding metals and including asilver or gold core. Because the reverse wound portion of conductor 51serves as electrode 53, an outer surface of the reverse wound portion ofconductor 51, as well as outer surfaces of all reverse wound portions ofconductors forming electrodes in various embodiments presented herein,must be suitable for this purpose; a platinum or platinum iridiumsurface is one example of a suitable electrode surface known to thoseskilled in the art. In one embodiment, a platinum clad wire is used forconductor 51, in another embodiment a platinum-iridium wire is used and,in yet another embodiment, a platinum surface is formed, for example, bysputtering platinum over reverse wound portion of conductor 51 formingelectrode 53.

[0015]FIG. 1B is a plan view of a multi-conductor coil 60 according toone embodiment of the present invention. Coil 60 is incorporated into anembodiment of a medical electrical lead according to the presentinvention as illustrated in FIG. 3. As illustrated in FIG. 1B coil 60includes a first wound conductor 61, a second wound conductor 62,forming an outer diameter 63 of coil, and an electrode 64 at a firstdistal end 65; first conductor 61 includes a reverse wound portionforming electrode 64, over outer diameter 63, and second conductor 62extends beyond electrode 64 to a second distal end 66. Coil 60 may beformed using a programmable coil winder, known to those skilled in theart, winding conductors 61 and 62 in first direction “A” and thenreverse winding first conductor 61 in second direction “B” to formelectrode 64, while continuing to wind second conductor 62 in direction“A” to second distal end 66. It should be noted that an outer diameterand pitch of coil 60 between first distal end 65 and second distal end66 need not be the same as a pitch or outer diameter 63 of coil 60indicated proximal to electrode 64. According to one embodiment of thepresent invention, second conductor 62 is joined to an electrode tip atsecond distal end 66, such as tip electrode 37, illustrated in FIG. 3,therefore second conductor 62 must be electrically isolated from firstconductor 61. Either first conductor 61 or second conductor 62, or both,include an outer insulative layer according to embodiments of thepresent invention, such insulative layers being described in conjunctionwith FIG. 1D.

[0016]FIG. 1C is a plan view of a multi-conductor coil 70 according toanother embodiment of the present invention. Coil 70 is incorporatedinto an embodiment of a medical electrical lead according to oneembodiment of the present invention as illustrated in FIG. 4. Asillustrated in FIG. 1C, coil 70 includes a first wound conductor 71, asecond wound conductor 72, a third wound conductor 73, and a fourthwound conductor 74, all forming an outer diameter 75; coil 70 furtherincludes a first electrode 76, a first intermediate electrode 77, and asecond intermediate electrode 78. First electrode 76 is formed byreverse winding first conductor 71 over outer diameter 75 at a firstdistal end 79 and fourth conductor extends to a second distal end 80. Inbetween first distal end 79 and second distal end 80 second and thirdconductors 72 and 73 are reverse wound to form first and secondintermediate electrodes 77 and 78 over outer diameters 75′ and 75″,respectively, as illustrated in FIG. 1C. In one embodiment diameters 75′and 75″ are approximately equal to diameter 75, however in an alternateembodiment diameter 75′ is smaller than diameter 75 and diameter 75″ issmaller than diameter 75′. Coil 70 may be formed in generally the samemanner described for coil 60 illustrated in FIG. 1B. According to oneembodiment of the present invention, fourth conductor 62 is joined to anelectrode tip at second distal end 80, such as tip electrode 37illustrated in FIG. 3 or tip electrode 95 illustrated in FIG. 4. Eachconductor 71-74, corresponding with different electrodes must beelectrically isolated from one another; according to one embodiment ofthe present invention, as illustrated in FIG. 1D, each conductor 71-74includes an outer insulative layer 101-104.

[0017]FIG. 1D is a partial section plan view of the multi-conductor coilillustrated in FIG. 1C. A section through each conductor 71-74 in asegment 100 of coil 70, proximal to first electrode 76, is illustratedin FIG. 1D, shows insulative layers 101, 102, 103, and 104. According toembodiments of the present invention, insulative layers 101-104 areformed form a biocompatible, biostable, and durable insulative material,one example of which is a polyamide. Although all four conductors areillustrated in FIG. 1D as having an insulative layer, in an alternateembodiment, one of the four may be without an insulative layer. Surfacesof reverse wound portions of conductors 71, 72, and 73, are freed ofinsulative layers 101, 102, and 103 in order to form electrodes 76, 77,and 78 respectively. According to one embodiment of the presentinvention, a laser is used to remove the layers 101-103 away from theouter surfaces of conductors 71-73 according to methods well know tothose skilled in the art.

[0018]FIG. 2A is a partial section plan view of an implantable lead 10incorporating coil 50 from FIG. 1A, according to one embodiment of thepresent invention. As illustrated in FIG. 2A, lead 10 further includes aproximal end 30, a distal end 26, an outer insulative sheath 22, aninner tubing 23 forming a lumen 25. As illustrated in FIG. 2A, coil 50extends around inner tubing and within outer insulative sheath 22 from aconnector contact 31 at proximal end 30 to distal end 26 where electrode53 is formed by reverse winding of conductor 51, as previouslydescribed, is disposed. In one embodiment, a fiber core 21, indicated bya dashed line, extends within lumen 25 from proximal end 30 to distalend 26 to strengthen lead 10; Williams and Chivers disclose embodimentsof leads having a fiber core construction in U.S. Pat. No. 6,516,230,which is incorporated herein in its entirety. In an alternateembodiment, a stylet (not shown) is used to guide lead 10 via lumen 25to an implant site and, in yet another embodiment, as illustrated inFIG. 2B, lumen 25 surrounds another conductor attached to a tipelectrode. FIG. 2B is a cross-sectional plan view of a distal end of analternate embodiment of a lead incorporating coil 50 from FIG. 1A. Asillustrated in FIG. 2B, lead 15 further includes a cable conductor 32extending from a proximal end (not shown), where it is joined to asecond connector contact (not shown), through lumen 25 past distal end26 of coil 50, where electrode 53 is formed, to a second distal end 16where it is joined to a helical tip electrode 24. According toembodiments of the present invention, cable conductor 32 is joined tohelical tip electrode 24 by means of welding, crimping, bonding with aconductive adhesive, or a combination thereof according to methods wellknown to those skilled in the art. As further illustrated in FIG. 2B,lead 15 includes an insulative spacer 27 electrically isolating tipelectrode 24 from reverse wound electrode 53. Although tip electrode 24is illustrated as a helix in FIG. 2B, various geometries of tipelectrodes well known to those skilled in the art are contemplated foralternate embodiments of the present invention.

[0019]FIG. 3 is a cross-sectional plan view of a distal end of analternate embodiment of a lead incorporating coil 60 from FIG. 1B. Asillustrated in FIG. 3, a lead 35 includes coil 60 extending around innertubing 23 and within outer insulative sheath 22 from a proximal end (notshown), where conductors 61 and 62 are each joined to a connectorcontact (not shown), to first distal end 65, where reverse woundelectrode 64 is formed by conductor 61, and to second distal end 66,where conductor 62 is joined to a tip electrode 37. Lead 35 furtherincludes an insulative spacer 38 including a set of tines 39 as afixation means to hold tip electrode 37 at the implant site according toone embodiment of the present invention. In an alternate embodiment ahelical electrode, such as electrode 24 illustrated in FIG. 2B, notrequiring tines 39 since a helical construction provides fixation, isjoined to conductor 62 at second distal end 66. Furthermore, anembodiment according to the present invention includes a tip electrode,such as tip electrode 37, without tines 39 or another fixation means.According to embodiments of the present invention, conductor 62 isjoined to tip electrode 37 by means of welding, crimping, bonding with aconductive adhesive, or a combination thereof according to methods wellknown to those skilled in the art. According to one embodiment, lead 35further includes fiber core 21 shown as a dashed line; fiber core 21serves to strength lead 35 as previously described in conjunction withFIG. 2A

[0020]FIG. 4 is a partial section plan view of a lead incorporating coil70 from FIG. 1C-D according to one embodiment of the present invention.As illustrated in FIG. 4, a lead 45 includes coil 70 extending aroundinner tubing 23 and within outer insulative sheath 22 from a proximalend 90, where conductors 71, 72, 73, and 74 are joined to connectorcontacts 91, 92, 93, and 94, respectively, to first distal end 79, wherereverse wound electrode 76 is formed by conductor 71, and to a seconddistal end 80, where conductor 74 is joined to a helical tip electrode95. In between first distal end 79 and second distal end 80, as furtherillustrated in FIG. 4, first intermediate electrode 77 and secondintermediate electrode 78 are formed by reverse wound conductors 72 and73, respectively, and insulative spacers 115, 116, and 117 arepositioned between electrodes 76 and 77, 77 and 78, and 78 and 79,respectively. According to embodiments of the present invention,conductor 74 is joined to helical tip electrode 95 by means of welding,crimping, bonding with a conductive adhesive, or a combination thereofaccording to methods well known to those skilled in the art. Althoughtip electrode 95 is illustrated as a helix in FIG. 4, various geometriesof tip electrodes well known to those skilled in the art arecontemplated for alternate embodiments of the present invention.

[0021] In various embodiments of the leads presented in FIGS. 2A-4,outer insulative sheath 22, inner tube 23, and insulative spacers 27,38, 115, 116, and 117 are formed from biocompatible and biostableinsulative materials, examples of which are polyurethane and silicone.Fabrication and assembly methods for such sheaths, tubes, and spacersare well known to those skilled in the art of electrical leadconstruction. Lengths of electrodes and spacers depicted herein varyaccording to different embodiments of leads, examples of which will beschematically presented in FIGS. 5-8. A maximum outer diameter ofembodiments range from approximately 0.025 inch to approximately 0.120inch depending upon an inner diameter required for lumen 25 and adiameter of the wound conductor wires. It is contemplated that variouslead constructions according to the present invention will includeconductors including wires having diameters ranging betweenapproximately 0.001 inch and approximately 0.010 inch, dependent uponelectrical resistance requirements. Furthermore, in one embodiment across-section of conductor wires is substantially round while in analternate embodiment a cross-section of conductor wires is substantiallyrectangular.

[0022] An inner diameter of lumen 25, for various embodiments accordingto the present invention, will range between approximately 0.005 inchand 0.050 inch; the inner diameter dependent upon the incorporationwithin lumen 25 of additional conductors or an elongated delivery tool,for example, a stylet, guide wire, or pull wire, or upon pressurerequirements for delivery of agents, for example a drug or a contrastagent, through lumen 25. In the latter case, if lumen 25 is used todeliver an agent an opening in lumen is included in proximity to adistal end of the lead.

[0023] FIGS. 5-8 are schematics depicting several embodiments ofimplantable leads according to the present invention joined to animplantable medical device 200 and implanted in exemplary locationswithin a heart 300. As illustrated in FIG. 5, a lead 400 includes a tipelectrode 401 and a reverse wound electrode 402 including a length 406and spaced at a distance 405 from tip electrode 401. In one embodimentlead 400 incorporates coil 50 of FIG. 1A and in an alternate embodimentlead 400 incorporates coil 60 from FIG. 1B. According to embodiments ofthe present invention, length 406 is between approximately 2 millimetersand approximately 6 centimeters and distance 405 is between 4millimeters and approximately 15 millimeters. According to oneembodiment of the present invention, length 406 of reverse woundelectrode 402 and spacing 405 are appropriate for electrode 402 to serveas a pace/sense anode in conjunction with tip electrode 401 (cathode),and, according to another embodiment length 406 and spacing 405 areappropriate for reverse wound electrode 402 to serve as a defibrillationelectrode.

[0024] As illustrated in FIG. 6, a lead 500 includes a tip electrode501, a first reverse wound electrode 502, including a length 506 andspaced at a distance 505 from tip electrode 501, and a second reversewound electrode 503, including a length 508 and space at a distance 507from first reverse wound electrode. In one embodiment, lead 500 includesa coil including a first and second conductor wherein both conductorsare reverse wound, having a configuration similar to lead 15 shown inFIG. 2B in that tip electrode 501 is joined to a cable conductor; inanother embodiment lead 500 includes a coil including a first, secondand third conductor, having a configuration similar to lead 45 shown inFIG. 4 in that first and second conductors form reverse wound electrodes503 and 502 while third conductor is joined to tip electrode 501.According to embodiments of the present invention, electrodes 502 and503 have lengths 506 and 508 between approximately 2 millimeters andapproximately 6 centimeters; distance 505 is between approximately 4millimeters and approximately 10 millimeters; and distance 507 isbetween approximately 1 millimeter and 5 millimeters. According to oneembodiment of the present invention, length 506 of electrode 502 is anddistance 505 are appropriate for electrode 502 to serve as a pace/senseanode in conjunction with tip electrode 501 (cathode) and length 508 ofelectrode 503 and distance 507 are appropriate for electrode 503 tofunction as a defibrillation electrode. According to another embodiment,as illustrated in FIG. 7, distance 507 is increased so that reversewound electrode 503 may positioned in another chamber of heart 300 orproximal to heart.

[0025] As illustrated in FIG. 8, a lead 700 includes all the elements oflead 500 from FIGS. 6 and 7 and further includes a third reverse woundelectrode 704 spaced at a distance 705 from second reverse woundelectrode 503 according to one embodiment of the present invention. Inone embodiment lead 700 incorporates coil 70 of FIG. 1C. Distance 705 issuch that reverse wound electrode may be positioned in an area of heart300 separate from an area in which tip electrode 501 is positioned.

[0026] Finally, it will be appreciated by those skilled in the art oflead construction and implantation that the present invention can takemany forms and embodiments and be applied in many more implant sitesthan those represented in FIGS. 5-8, such as epicardial sites andneuro-stimulation sites. The true essence and spirit of this inventionare defined in the appended claims, and it is not intended that anyembodiment of the invention presented herein should limit the scopethereof.

What is claimed is:
 1. An implantable lead comprising: an insulativesheath; and a coil member extending through the insulative sheath andincluding a wound conductor, a proximal end, a first distal end, areverse wound electrode, and a first outer diameter; wherein theconductor winds from the proximal end to the first distal end formingthe first outer diameter of the coil member, and reverse winds backtoward the proximal end to form the electrode on the first outerdiameter, the electrode disposed adjacent and distal to the insulativesheath.
 2. The implantable lead of claim 1, wherein the wound conductorincludes a plurality of common wires, the plurality including from twoto six wires.
 3. The implantable lead of claim 1, wherein a length ofthe electrode is between approximately 2 mm and 3 cm.
 4. The implantablelead of claim 1, wherein a length of the electrode is betweenapproximately 3 cm and 6 cm.
 5. The implantable lead of claim 1, whereinthe electrode serves as a pacing and sensing anode.
 6. The implantablelead of claim 1, wherein the electrode serves as a defibrillationelectrode.
 7. The implantable lead of claim 1, wherein the insulativesheath includes an outer diameter and the electrode forms a second outerdiameter of the coil member, the second outer diameter substantiallyequivalent to the outer diameter of the insulative sheath.
 8. Theimplantable lead of claim 1, further comprising an electrode tippositioned at a second distal end, the second distal end disposed distalto the first distal end; wherein the coil member further includes asecond wound conductor winding from the proximal end to the seconddistal end further forming, proximal to the first distal end, the firstouter diameter of the coil; the second conductor including an outerinsulative layer and coupled to the electrode tip.
 9. The implantablelead of claim 8, wherein the wound conductor and the second woundconductor each include a plurality of wires, the plurality including apair of wires.
 10. The implantable lead of claim 8, further comprisingan inner tubing forming a lumen and extending within the coil from theproximal end to the second distal end; and a fiber core extending withinthe lumen from the proximal end to the second distal end where it isjoined to the electrode tip.
 11. The implantable lead of claim 8,wherein the coil member further includes a third wound conductor and afirst reverse wound intermediate electrode; the third conductorincluding an outer insulative layer and winding from the proximal end toa position in between the first distal end and the second distal endfurther forming the first outer diameter of the coil, and reversewinding back toward the proximal end to form the intermediate electrodeon the first outer diameter of the coil.
 12. The implantable lead ofclaim 11, wherein the coil member further includes a fourth conductorand a second reverse wound intermediate electrode; the fourth conductorincluding an outer insulative layer and winding from the proximal end toa position in between the first intermediate electrode and the seconddistal end further forming the first outer diameter of the coil andreverse winding back toward the proximal end to form the secondintermediate electrode on the first outer diameter of the coil.
 13. Theimplantable lead of claim 1, wherein the coil member further includes asecond wound conductor, a second distal end, disposed distal to thefirst distal end, and a second reverse wound electrode; the secondconductor including an outer insulative layer and winding from theproximal end to the second distal end further forming the first outerdiameter of the coil and reverse winding back toward the proximal end toform the second electrode on the first outer diameter of the coil. 14.The implantable lead of claim 1, further comprising an insulated cableconductor and an electrode tip positioned at a second distal end, thesecond distal end disposed distal to the first distal end; wherein thecable conductor is disposed within the coil member extending from theproximal end to the second distal end and coupled to the electrode tip.15. The implantable lead of claim 14, wherein a length of the electrodeis between approximately 2 mm and 3 cm.
 16. The implantable lead ofclaim 14, wherein a length of the electrode is between approximately 3cm and 6 cm.
 17. The implantable lead of claim 14, wherein the electrodeserves as a pacing and sensing anode.
 18. The implantable lead of claim14, wherein the electrode serves as a defibrillation electrode.
 19. Theimplantable lead of claim 14, wherein the insulative sheath includes anouter diameter and the electrode forms a second outer diameter of thecoil member, the second outer diameter substantially equivalent to theouter diameter of the insulative sheath.
 20. The implantable lead ofclaim 14, wherein the coil member further includes a second woundconductor and a first reverse wound intermediate electrode; the secondconductor including an outer insulative layer and winding from theproximal end to a position in between the first distal end and thesecond distal end further forming the first outer diameter of the coiland reverse winding back toward the proximal end forming the firstintermediate electrode on the first outer diameter of the coil.
 21. Theimplantable lead of claim 20, wherein the coil member further includes athird wound conductor and a second reverse wound intermediate electrode;the third conductor including an outer insulative layer and winding fromthe proximal end to a position in between the first intermediateelectrode and the second distal end further forming the first outerdiameter of the coil and reverse winding back toward the proximal endforming the second intermediate electrode on the first outer diameter ofthe coil.
 22. An implantable lead comprising, an insulative sheathincluding an outer diameter; an electrode tip; a coil member extendingthrough the insulative sheath including a first wound conductor, asecond wound conductor, a proximal end, a first distal end, a seconddistal end, an reverse wound electrode, a first outer diameter and asecond outer diameter; an inner tubing forming a lumen and extendingwithin the coil from the proximal end to the second distal end; and afiber core extending within the lumen from the proximal end to thesecond distal end where it is joined to the electrode tip; wherein thefirst conductor winds from the proximal end to the first distal endforming the first outer diameter of the coil and reverse winds backtoward the proximal end forming the electrode on the outer diameter ofthe coil, the electrode disposed adjacent and distal to the insulativesheath and forming the second outer diameter of the coil substantiallyequal to the outer diameter of the sheath; the second conductor includesan outer insulative layer and winds from the proximal end to the seconddistal end, the second distal end disposed distal to the first distalend, further forming, proximal to the first distal end, the outerdiameter of the coil; and the second conductor coupled to the electrodetip at the second distal end.
 23. A method of manufacturing animplantable lead comprising the steps of: winding a conductor to form acoil member, the coil member including a proximal end, a distal end, andan outer diameter; and reverse winding the conductor from the distal endback toward the proximal end over the outer diameter of the coil member.